The present invention relates to control devices and, more specifically, joystick devices for controlling heavy machinery.
It is not uncommon for a piece of heavy machinery to be controlled by a joystick device. In such an arrangement, an operator grasps the joystick device and uses the device to steer the machine or perform other functions. Additionally, the joystick device may contain input buttons that allow the operator to control other functions of the machine. For example, in a lift truck, the joystick device may contain input buttons to allow the operator to control the movement and positioning of the lift arms.
The disadvantage of these joystick devices is that they require a plurality of electrical connections. Each of the input sources, including any input buttons and the grip itself, require electrical connections. Typically, each input requires power and ground connections to supply power as well as a data connection for sending an output signal to a remotely located main controller. As a result, conventional joystick devices typically employ many wires and cables, which tend to be bulky and compromise space.
U.S. Pat. No. 6,550,562 to Brandt et al. discloses a joystick controller that pivots from side to side and from front to back. In addition, the Brandt et al. device has a plurality of input buttons that control other functions of the vehicle, such as the turn signals, horn, and specific movements of the lift arms. All of these input buttons are electronically connected to a microprocessor disposed within the grip. The microprocessor combines all of these inputs and sends a single serial communication signal to a remotely located main controller that controls and drives the lift truck or other heavy machinery.
As described above there are many types of manufactured joysticks. Of current joystick devices, some utilizes two hall effect sensors per axis to create redundant sensing. However, to date the information from these redundant sensors is processed remotely from the joystick itself. This remote processing is disadvantageous where the electronic device is susceptible to failures. In the case of failure the device can either send out a signal that indicates an error or it can send out a false or bad signal that is within the normal expected operating range. This second type of signal presents a problem to the system in which the electronic device is being used because the system cannot distinguish if the signal is actually being commanded by the system or if it is a false signal. In the case of an electronic joystick used in conjunction with a remotely located micro controller and a vehicle as part of a system, the consequences of this type of failure (when the joystick fails and sends out a false or bad signal that is within the operating range, but is not the signal that is being commanded) result in an unsafe condition. Thus there exists a need in the art for a joystick that prevents this type of failure which creates unsafe conditions.
It is therefore a principal object of this invention to provide a joystick device that uses redundant sensors and an onboard microprocessor to determine if a failure of the device has occurred.
A further object of this invention is to provide a joystick device that has the ability to safely discontinue the joystick's function.
Another object of this invention is to provide a joystick device that has the ability to continue to operate the joystick and send out an error message to indicate that the signal is no longer verifiable.
These and other objects will be apparent to those skilled in the art.